In this paper we present the Coupled Active Contours
(CAC) method, which is applied to segmentation
of the endocardium in ultrasonic images assuming
Rayleigh distributed intensities. Comparative experiments,
both real and synthetic, with a standard prior
model are presented. In the CAC model the prior acts,
by affine transformation, on the same image information
as the active contour, in addition to the traditional
interaction between prior and active contour. By this
higher convergence rate and robustness, w.r.t artifacts
and poor initialization, is achieved.